The idler wheel of a generic tracklaying gear disclosed in WO 03/018388 A comprises an outer part with a U-shaped cross-section consisting of individual segments, and an inner part mounted to be rotatable about the axis which engages, with a thickened outer rim, the U-groove of the outer part from the inside. Each segment is movably fixed in the thickened rim via two axial pins. On both sides of a centric surrounding collar at the outer side of the rim, elastomer rings of an approximately rectangular cross-section are inserted with pre-tension and relatively movably support the outer part on the inner part with a radial as well as an axial clearance on both sides. Due to the pre-tension of the elastic rings, these have load-transmitting abilities in the axial as well as in the radial direction. There is no direct, exclusively radial sliding guide between the inner and the outer parts. The transverse pins fixing the segments form a drive type fastening between the outer and the inner parts with a form-fit in the circumferential direction.
In the idler wheel or the drive chain wheel of the generic tracklaying gear disclosed in U.S. Pat. No. 3,730,013 A, the respective outer annular part is connected with the inner, hub-like part only via pretensioned elastomer rings inserted between them. In the inner part, at an axial side, a pendulum balancing system with rolling elements distributed in the circumferential direction and with a ring radially movable relative to the inner part by the rolling elements is provided. In addition to the damping rings between the outer and the inner parts, on the outer parts, additional external elastomer rings are inserted in positioning grooves.
In the idler wheel of a tracklaying gear of US 2010/0141026 A, at the circumferential flange of the inner part, ring bodies are externally fixed on both sides by means of straining screws which project with broadened shoulder parts to the outside beyond the outer periphery of the peripheral flange and receive a base part of an outer ring with a T-shaped cross-section between them such that the inner diameter of the base part has a radial clearance to the outer diameter of the peripheral flange. In positioning grooves of the two ring bodies opened to the outside, elastomer rings are inserted on both sides of the base part which are pre-tensioned such that they obtain load-transmitting abilities and transmit radial as well as axial loads. The inner walls of the ring bodies are tensioned against the outer walls of the peripheral flange of the inner part, while the outer walls of the base part of the outer ring each maintain an axial clearance to the inner walls of the ring parts, so that the outer ring is centered by the pre-tensioned elastomer rings radially and axially with respect to the inner part. The degree of the axial clearance can be between 0.5 to 2.0 mm per side, so that the outer ring can have an axial moving part with respect to the inner part of up to 4.0 mm and thus no exclusively relative sliding guide is given.
In an idler wheel disclosed in JP 56138068 A, two outer parts are circumferentially mounted on the periphery of the inner metallic part such that they define a circumferential groove between them which is open to the outside. In the circumferential groove, a pressurized elastomer hose is provided between the inner walls of the outer parts and the outer periphery of the inner part, the hose acting upon an annular member radially to the outside and against a joint sleeve of a track joint, the annular member being of a material worn by friction which is different from the metal material of the inner and outer parts. The annular member has an H-section and can enlarge or reduce its radius in adaptation to an expansion or contraction of the pressure hose.
In a tracklaying gear of U.S. Pat. No. 5,758,932 A, instead of standardized circumferential teeth, a profiling is attached at the outer periphery of the drive chain wheel which is designed similar to the tread of a wet tire and which has diamond-shaped elevations to engage with the caterpillar track and channels situated in-between to discharge penetrated impurities. This circumferential teeth structure is either formed of the metal material of the drive chain wheel, or it is attached by welding or casting and thus consists of a metallic material. Also due to the polygon effect in the driving operation of the tracklaying gear, the caterpillar track or the links of the caterpillar track cyclically hit the drive chain wheel which generates loud noise and undesired wear.
In a tracklaying gear of a road finishing machine disclosed in EP 2 050 664 A, a solid rubber jacket is vulcanized onto the circumference of the metallic idler wheel, via which the idler wheel is in contact with the caterpillar track. The solid rubber jacket must take on the total load and transmit it to the metallic part of the idler wheel which can result in strong wear and a floating driving feel.
In a tracklaying gear disclosed in US 2007/0029878 A, the idler wheel and the drive chain wheel are completely fabricated of metal, and the load is transmitted into the running gear suspension via metallic contact surfaces, so that the inevitable impacts of the caterpillar track lead to the generation of loud noise.
In the tracklaying gear shown in U.S. Pat. No. 3,647,270 A, the drive chain wheel (tumbler) and the idler wheel are metallic, resulting in loud running noise.
EP 0 721 879 B1 discloses two external, axially separated rubber linings in an idler wheel.
US 2002/0113489 A discloses ring segments at the circumference of a running wheel of a tracklaying gear which are coupled to the hub part via transverse pins contained in rubber sleeves. The rubber sleeves are placed in saucer-type recesses in the ring segments in the circumference of the hub part. The ring segments are movably coupled to one another via transverse pins. A radial guidance of the outer lining of this running wheel is not possible.
DE 3 537 665 A relates to a multi-part idler or running wheel for tracklaying gears wherein between the inner and outer parts of the running wheel, two annular damping layers are inserted and a raised guide collar is provided in the center, and bearing shoulders are provided on both sides. There is no clear radial guidance.
DE 2 617 342 A discloses a tumbler in which between two outer crown gears which are rigidly connected to the hub, two rubber linings are externally attached on the hub on which the caterpillar track can support itself and between which a guiding indentation for the lateral guidance of the caterpillar track is kept clear.
The object underlying the present invention is to provide a tracklaying gear of the type mentioned above which is characterized by low operating noises in the driving operation with a stable guidance of the caterpillar track.